Plants that live under the water, such as sea grasses, produce oxygen for fish and other aquatic life, as well as provide food, shelter, nurseries and habitat. Like any plant, seagrasses need sunlight to produce energy in a process called photosynthesis. When the lagoon becomes murky, light is not able to penetrate the water very far and if the seagrass are unable to photosynthesize for long enough they die. Each time the lagoon loses some seagrass it loses all the fish and shellfish that would have thrived there. Since the 1940s the Indian River Lagoon has lost over 10,000 acres of sea grasses with an economic value of over 14 million dollars a year. The economic loss since the 40s, totals $880 million due to reduced water quality. Secchi depth is a method for measuring the penetration of light below the surface of the water. The method uses a Secchi disk with a checkerboard pattern of four alternating black and white painted quarters with a pre-measured line attached. The disk is lowered into the water until it can no longer be seen from the surface or the black can be no longer distinguished from white areas. This depth is known as the Secchi depth. Low Secchi depths usually are caused by large amounts of suspended materials or natural or man-made chemicals dyeing the water a dark color. The higher the secchi depth the deeper the seagrass can survive. The goal for water clarity in the Indian River Lagoon is one and a half meters (almost five feet). If this goal could be reached then large areas of the lagoon would grow seagrasses where currently there is little or none. Unfortunately this goal is usually not reached even during a drought period. The series of maps to the right show the average monthly secchi depth found by volunteers in the Lagoon Watch. Last May, large portions of the lagoon showed very high secchi depths (dark blue), most likely as the result of the drought. By July from Cocoa to the Fort Pierce Inlet got worse while some areas south and north did improve. This could be related to a break in the drought bringing in sediment and fertilizers. The combination of warm sunny days and the nutrients from fertilizers fuel algal blooms which cloud the water. Water clarity continued to decline through September and November, even as temperatures cooled off, reducing the likelihood of algal blooms. Conditions were particularly bad in November just south of Titusville in Brevard and also in the St Lucie River. Overall rainfall was not very high during this period but wind, especially from storms can still stir up fine sediment(muck) on the bottom of the lagoon and its tributaries and reduce water quality. When sandy sediment is stirred up it settles out of the water column in a few hours at most. Fine muck sediments can take as long as two weeks to settle out, leaving the water murky and unable to transmit light to seagrasses. Water clarity improved in Martin, St Lucie and Indian River Counties in January and improved in Brevard in March and May of 2002. Currently the water clarity in the Lagoon is over three feet in many places but still short of our five foot goal.